Stitch-forming mechanism for sewing machines



- Jan. 22, 1935. A. GRIEB STITCH FORMING MECHANIS FOR SEWING MACHINES |Filed Nov. 28. 1933 Patented Jan. 22, 1935 UNITED STATES PATENT OFFICE STITCH-FORMING NIECHANISM FOR SEWING MACHINES Alfred Grieb, Elizabeth, N. J., assignmto The Singer Manufacturing Company,

Elizabeth,

This invention relates to improvements in lockstitch sewing machines and more particularly to improvements in sewing machine loop-taker and thread-case combinations designed to cast loops of needle-thread about an interlocking thread housed within the thread-case.

The primary object of the present invention is to insure the formation of perfect lock-stitches, i. e., stitches in which the needle-thread spirals continuously in the same direction about an interlocking thread, by a sewing machine having a loop-taker journaled for rotation about an axis substantially parallel to the direction of feed. A further object of the invention is to provide for pulling 011 short lengths of the interlocking thread by means of a pull-01f member carried by a loop-taker, without incurring any liability of breakage of the interlocking thread should the loop-taker be inadvertently turned in a retrograde direction, as may occur for instance when the sewing machine is treadle-operated.

With these and other objects of the invention in view, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawing of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

In the accompanying drawing, Fig. 1 is a front elevation of the improved horizontal-axis rotary loop-taker in a position thereof wherein the pullof flange at the tail of the hook begins to pull off the interlocking thread. Fig. 2 is a side elevation and Fig. 8 a top plan of the loop-taker in a position wherein the tail of the loop-taker has just passed the portion of the interlocking thread leading to the throat-plate needle-aperture.

Referring to the drawing, the present improvements have been embodied in a sewing machine constructed substantially as disclosed in a U. S. patent application of George M. Eames, Serial No. 691.938, filed Oct. 3, 1933. The sewing machine has a vertically reciprocatory and laterally vibratory needle 1, and the machine may be employed for making either zigzag or straightaway stitch seams The work is supported by a throat-plate 2 provided with the usual feed-slots 3 for a work-advancing feed-dog 4, said throatplate also having a needle-aperture 5 which, in the present case, is elongated transversely of the line of feed to acommodate lateral vibrations of the needle 1.

Cooperating with the needle 1, in the formation of lock-stitches, is a rotary loop-taker 6 disposed below the throat-plate 2 and preferably of the rotary hook type. The loop-taker 6 is carried by a horizontally disposed loop-taker shaft 7 having its axis disposed substantially in a vertical plane containing the line of feed of the work and the needle-path of reciprocation, said loop-taker having a cup-shaped body provided at the outer edge of its periphery with a needle-thread loop seizing beak 8 and a loop-discharging tail or spur 9 adjacent and directed oppositely to the beak 8. Opposite to the beak 8, the peripheral edge of the loop-taker curves outwardly to form an interlocking-thread pull-off member or flange 10 provided with a. needle clearance slot 11. The outwardly flaring or thread pull-off edge of the flange 10 merges into an inwardly curving or interlocking-thread-releasing free end 12 which is disposed substantially diametrically opposite to the beak 8, but at the side of the needle-path opposite to the path of said beak 8.

J ournaled in the loop-taker 6 is a thread-case which is preferably made in separable sections comprising a holder-section 13 and a cap-section 14 which are secured together by a latch 15 and confine therebetween an interlocking-thread bobbin 16. Suitably secured upon the periphery of the cap-section 14 is a tension-spring 17 for the interlocking thread b which then passes to an open thread-delivery eye 18 provided in the outer face of the cap-section 14 by suitably slotting said outer face. According to the present improvement, the thread-delivery eye 18 is located at one side of a vertical plane containing the axis of rotation of the loop-taker and at the side of said plane at which the loop-taker begins to cast a loop of needle-thread a about the thread-case. Accordingly, the interlocking thread b passes to the throat-plate needle-aperture 5 at an inclination to and from one side of the needle-path of reciprocation. The described location of the thread-delivery eye 18 therefore insures that the needle will uniformly descend at the same side of the interlocking thread I) in the production of straightaway-stitch seams, thereby obviating the formation of imperfect or so-called hitchstitches in a forward feed of the work.

The thread-case is restrained against rotation with the loop-taker by providing the holdersection 13 at the upper portion of its outer face with a stop-notch 19 entered by a stationary stopfinger 20 secured to the machine frame in any suitable manner (not shown). According to the present improvement, the stop-notch 19 is also disposed at one side of a vertical plane containing the axis of rotation of the loop-taker 8, but at the side of said plane opposite to the thread-delivery eye 18. By this disposition of the stopnotch 19, it is so far removed from the length or the interlocking thread b between the threadeye 18 and the throat-plate needle-aperture 5 as to entirely obviate any liability that the thread 17 will be wiped into said stop-notch by the loop of needle-thread a cast about the thread-case by the loop-taker, thus insuring the desired lead of the interlocking thread b from one side of the needle-path.

A further advantage residing in the described location or the stop-notch 19 is that thereby the portion 13' of the thread-case holder-section 13 at one side of the stop-notch 19 extends axially outwardly beyond the path of the free end 12 of the pull-oiI flange 10, said thread-case portion 13" thereby serving to hold the thread b outwardly sufficiently far to clear the end 12 or the pull-ofl flange and obviating any liability that the interlocking thread will be caught and broken by the flange end 12 in any retrograde rotation of the loop-taker.

Having thus set forth the nature of the invention, what I claim herein is:-

1. In a sewing machine, in combination, a vertically reciprocatory needle, a throat-plate having a needle-aperture, a work-advancing teed-dog, a rotary loop-taker having its axis of rotation substantially parallel to the line of feed, a threadcase for an interlocking thread disposed within said loop-taker and provided with a stop-notch at one side of a vertical plane containing the line of feed and the needle-path of reciprocation, said thread-case having a thread-delivery eye at the opposite side of said plane for directing the interlocking thread over the outer face or the threadcase at one side of said stop-notch to the throatplate needle-aperture, a stationary stop-finger entering the stop-notch oi. said thread-case, and a pull-oi! member carried by said loop-taker to engage and pull of! short lengths of said interlocking thread.

2. In a sewing machine, in combination, a vertically reciprocatory needle, a throat-plate having a needle-aperture, a work-advancing teeddog, a rotary loop-taker having a needle-thread loop-seizing beak and an interlocking thread pullofi member terminating in a free end substantially diametrically opposite to said loop-seizing beak, a thread-case for an interlocking thread disposed within said loop-taker and provided in the loop cast-oi! side of its outer face with a stop-notch, said thread-case having a thread-delivery eye at the loop cast-on side thereof for directing the interlocking thread over the outer face of the thread-case at one side 01. said stopnotch to the throat-plate needle-aperture, and a stationary stop-flnger entering the stop-notch of said thread-case.

3. In a sewing machine, in combination, a vertically reciprocatory needle, a throat-plate having a needle-aperture, a work-advancing feeddog, a rotary loop-taker having a needle-thread loop-seizing beak and an interlocking-thread pull-off flange terminating in a free end at the side of the needle-path oi reciprocation opposite to the path of the loop-taker beak, said looptaker having its axis of rotation substantially parallel to the line of feed, a thread-case'for an interlocking thread disposed within said looptaker and provided with a stop-notch at one side of a vertical plane containing the line of feed and the needle-r th of reciprocation, the outer face of said thri id-case adjacent to said stop-notch extending axially outwardly beyond the path of the free end of said flange, said thread-case having a thread-delivery eye at the opposite side of said plane for directing the interlocking thread over the outwardly extending portion of the thread-case to the throat-plate needle-aperture, and a stationary stop-finger entering the stopnotch of said thread-case.

ALFRED GRIEB. 

